As a method for obtaining a material which is excellent in terms of chemical and physical properties such as a catalytic activity and adsorptivity, a method in which a microporous substrate is coated with an organic or inorganic coating material and a method in which a coated material formed by a coating step is peeled off to obtain a microporous-surfaced material having on its surface an inverted configuration of the microporous configuration of the substrate is known.
In such a method, a coating material such as a sol or gel is coated on a surface of a substrate. However, this method involves a problematic closure of a micropore opening with the coating material when the substrate has a micropore whose diameter is less than a micron order(.mu.m).
Accordingly, the coating material can not be penetrated into the innermost of the micropore, resulting in difficulty in obtaining an intended microporous-surfaced material effectively.
On the other hand, a method in which a coating material is coated onto a substrate by means of a gaseous phase method such as CVD is also proposed. However, in this method, a prolonged time period is required to allow the vapor of the coating material to be penetrated into the micropore. Especially in the case of a material having a low vapor pressure, only a small amount can be vaporized and the coating time is extremely prolonged.
In an attempt to overcome the problems mentioned above, a method in which a supercritical fluid containing a polymeric material dissolved therein is brought into contact with an inorganic porous membrane is proposed (Japanese Laid-Open Patent Publication No. 7-144121). Also a method is known in which a supercritical fluid containing a ceramic precursor such as a polycarbosilane or a polysilane dissolved therein is impregnated in a carbon/carbon complex where it is allowed to precipitate and then subjected to a heat treatment to form a ceramic membrane of SiC, SiN and the like on its surface thereby heightening its oxidation resistance (Japanese Laid-Open Patent Publication No. 1-308873).
Nevertheless, the methods disclosed in the publications described above involve, similarly as in the former two methods, the problematic closure of a micropore opening with the polymeric material when the micropore has a diameter less than a micron thereby preventing the supercritical fluid containing such a material from being penetrated sufficiently.
As a result, an intended coating can not be achieved.
An objective of the present invention is to overcome such conventional problems by providing a coated material and a method for producing the same, by which a coated material formed by coating the surface of a substrate efficiently with a reaction product can be obtained, and also by which a reaction product transferring or reproducing the microstructure of the substrate can be obtained after removing a part or all of the substrate from the coated material.